linux-kernel - Re: Wait for console to become available, v3.2

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Message-ID: <alpine.LFD.2.00.0904211016190.2199@localhost.localdomain>
Date:	Tue, 21 Apr 2009 10:31:48 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	David Woodhouse <dwmw2@...radead.org>
cc:	David Brownell <david-b@...bell.net>, alan@...rguk.ukuu.org.uk,
	Ingo Molnar <mingo@...e.hu>,
	David VomLehn <dvomlehn@...co.com>,
	Arjan van de Ven <arjan@...radead.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux USB Mailing List <linux-usb@...r.kernel.org>,
	Linux Embedded Mailing List <linux-embedded@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Wait for console to become available, v3.2



On Tue, 21 Apr 2009, David Woodhouse wrote:
> 
> We can provide un-hooked-up /dev/console though. Rather than just
> failing to open it, why can't we make __tty_open() give you a dummy tty
> driver which is basically equivalent to /dev/null? And then 'replace' it
> with the real console driver if/when that later gets registered? The
> latter will be a high-caffeine job, but surely not impossible?

This sounds like a good option. 

Right now we look through all the console_drivers at open time in that

	struct tty_driver *console_device(int *index)

thing, but it should be possible to just do something like

	static struct tty_driver console_driver;

and then just make "console_device()" always return _that_ tty driver 
instead. Then, we could make that console_device tty driver just at 
run-time spread the IO to the proper device(s), rather than fix the one 
particular device at "open()" time.

[ Actually, looking closer we should not use that particular name: we 
  already have something called a "console_driver" which is really the 
  "current VT" driver.

  So we should call it 'system_console_device' or something, but you 
  get the idea. ]

Anybody want to try it? Just make it ignore any IO if there are no 
registered consoles. The patch shouldn't even be all that big, I suspect.

		Linus
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